Blade cascade and turbomachine

Abstract

A blade cascade for a turbomachine having a plurality of blades arranged next to one another in the peripheral direction, at least two blades having a variation for generating an asymmetric outflow in the rear area, as well as a turbomachine having an asymmetric blade cascade, which is connected upstream from another blade cascade, are disclosed.

Description

[0001]This claims the benefit of European Patent Application EP 12153623.9, filed Feb. 2, 2012 and hereby incorporated by reference herein.[0002]The present invention relates to a blade cascade for a turbomachine as well as a turbomachine.BACKGROUND[0003]In turbomachines, in particular in compressors and hydraulic pumps but also in turbines, instable flow states and greatly increased losses result during partial and overload operations. On the one hand, the instable flow states result in strong pressure fluctuations which may damage the blade structures. On the other hand, the flow may completely collapse in the compressors and hydraulic pumps in a throttled state. This limits the operating range of the turbomachine and may result in damage to the turbomachine when admissible limits are exceeded.[0004]The instable flow state is primarily caused by the flow separation on the individual blades in the cascade system. To suppress the separation, a temporarily changed inflow may lead tow...

AI Technical Summary

Benefits of technology

[0006]It is an object of the present invention to provide a blade cascade for a turbomachine which eliminates the above-mentioned disadvantages and increases the operating range of turbomachines compared to the known measures. Furthermore, it is an object of the present invention to provide a turbomachine having an increased operating range.

[0008]Due to the at least two different rear edge angles, the blade cascade is asymmetric in the peripheral direction, an asymmetric outflow taking place due to the variation in the rear blade area and thereby an inflow asymmetric in the peripheral direction with regard to a flow angle and flow moment being generated toward a downstream blade cascade affected by the separation. Viewed in the flow direction, the separation behavior in the blade cascade, which follows the asymmetric blade cascade, is suppressed thereby. The approach according to the present invention allows the operating range, in which a turbomachine may be operated, to be expanded and thus a reliable operation to be ensured even during partial and overload operations. Furthermore, the flow losses are reduced due to the asymmetric blade cascade according to the present invention and the efficiency is thus increased. The integration of the blade cascade into a turbomachine may take place without additional installations and with the aid of minor constructive measures. This allows the blade cascade to be used in already designed turbomachines without the need for redesigning the turbomachines. The asymmetric arrangement according to the present invention may be used in compressors or hydraulic pumps and in turbines as well as in machines through which a gaseous as well as a fluid medium flows. The blade cascade may, in addition, have an axial design, a radial design, or a mixed diagonal design.

[0014]Particularly good effects may be achieved when the arrangements of the blades in the peripheral direction, named above as an example, are continued periodically multiple times.

[0017]The turbomachine may have an adjusting device which staggers the blades to different degrees and which allows both the formation of a symmetric blade cascade and the formation of an asymmetric blade cascade. Ideally, the adjusting device allows each blade to be controlled individually, whereby the highest flexibility possible is achieved with regard to the stagger. Alternatively, however, predefined symmetries and asymmetries may be set, which considerably simplifies the setting of the particular blade cascade.

Problems solved by technology

In turbomachines, in particular in compressors and hydraulic pumps but also in turbines, instable flow states and greatly increased losses result during partial and overload operations.

On the one hand, the instable flow states result in strong pressure fluctuations which may damage the blade structures.

On the other hand, the flow may completely collapse in the compressors and hydraulic pumps in a throttled state.

This limits the operating range of the turbomachine and may result in damage to the turbomachine when admissible limits are exceeded.

The disadvantage of these active measures is, however, that, on the one hand, energy, which must be taken from the overall process, is needed to influence the flow, whereby the overall efficiency is reduced.

On the other hand, to implement these measures, complex constructive and regulative changes are necessary which result in an increased development effort, an increased susceptibility to errors, and an increased weight of the machine.

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